Current automotive vehicle windscreen cleaning and clearing systems are essentially based on the mechanical scrubbing and squeegee action of a flexible wiper blade on the windscreen surface. In essence, the conventional windshield wiper system makes no effort to prevent rain, snow, insects and other objectionable materials from striking the windshield surface; rather, the conventional windshield wiper system depends on periodically cleaning or clearing such materials from the windscreen surface. To assist in this function it is also known to spray the windscreen surface with cleaning and de-icing liquids by means of a reservoir and pump system carried on the vehicle.
The prior art also contains some limited recognition that flowing air can be used to clear a vehicle windscreen or rear window or to maintain a cleared condition once it has been achieved by another mechanism. For example, wind deflectors are commonly used in combination with vehicle top-mounted luggage racks to direct air flowing as a result of relative motion between a vehicle and ambient air downwardly over the backlight of the vehicle. In addition, U.S. Pat. No. 4,678,224 issued July 7, 1987 to Erwin F. Geppert discloses the use of plural discrete nozzles for the purpose of generating an air curtain on a military vehicle, which air curtain prevents the accumulation of airborne mud particles on small observation windows of the vehicle.
In addition, U.S. Pat. No. 1,717,904 issued June 18, 1929 to H. Abernethy discloses the use of an air curtain to clear and maintain the front windscreen of a trolley car. The Abernethy system comprises a pipe which is mounted so as to extend across the upper outside surface of the trolley windscreen. The pipe is provided with a plurality of discrete nozzles, non-uniformly spaced along the pipe, to direct a plurality of fan-shaped air blasts downwardly over and along the surface of the windscreen. A compressed air tank is mounted on and carried by the vehicle and may be supplied with air by the air brake system of the trolley.
The problems and disadvantages attending such prior art systems are generally well-known. Conventional windshield wipers are notorious for breakage, streaking and scoring of windscreen surfaces and, under heavy rain conditions, providing inadequate visibility as a result of the accumulation of water between clearing strokes. Use of conventional wipers for the removal of accumulated ice and frost from the outside surface of the windscreen is well-known to require by way of supplementation either manual scraping or extraordinary patience while the conventional interior heating system of the vehicle achieves an operative temperature. The Abernethy trolley car system, although interesting in concept, is aesthetically non-pleasing and hydrodynamically unfeasible for high speed vehicles.